Raising friendly brooder chicks

I have brooder of 8 precious chicks currently and I want to make sure they grow up friendly. I have a 10 year old little sister who wants to be very involved in helping me raise them and I want to make sure the chickens all grow up to be friendly and non-pecky towards her. My family members are very bad about coming outside to the brooder to pick them up and play with them, but I'm worried that this may be scaring the chicks more than anything. Are there any tips or guidelines we should follow to make sure they grow up happy and friendly? Thanks!!!